Therapeutic Hypothermia Becoming Standard of Care in Cardiac Arrest

For fans of TV medical dramas, reality can come as a shock. Week after week, they are accustomed to seeing defibrillators restoring flat lined heartbeats to happy ever afters.

Few would guess that until recently, only around six percent of cardiac arrest patients revived in Alabama survived to recover fully.

“Now we’re seeing 40 to 50 percent of revived patients at St. Vincent’s East walk out of the hospital with little or no neurological deficit,” Birmingham Heart Clinic cardiologist Jason Thompson, MD, said. “Some of that improvement is from more people learning CPR, and now more schools, churches and other places where people gather have automatic external defibrillators. However, the one change I’ve seen that is making the biggest difference is therapeutic hypothermia.”

Also known as targeted temperature management, the therapeutic hypothermia protocol cools the bodies of patients revived after cardiac arrest to between 32 °C (90 °F) and 34 °C (93 °F). A recent study found benefits in even more moderate cooling at temperatures as high as 36 °C (97 °F).

Hypothermia as a therapy following cardiac arrest is not a new idea. It was attempted in the 1950s with less than favorable results, primarily because the more profound cooling to much lower temperatures created its own complications. There was a resurgence of interest in the 1990s using much milder cooling.

“I was at Johns Hopkins when we were getting encouraging reports from Australia and Europe,” Thompson said. “When we started using the protocol and saw the results, we were enthusiastic, too.”

Without cooling, cardiac arrest often causes widespread cerebral ischemia leading to severe neurologic impairment. Hypothermia seems to improve survival by not only reducing cellular metabolism rates and the demand for oxygen, but also reducing reperfusion injury and damage from a cascade of reactions and inflammatory immune responses.

“Cooling the body and gradually rewarming helps to prevent damage,” Thompson said. “The sooner cooling can begin, the better—ideally within fifteen minutes if possible, but even up to six hours after an arrest, we see some benefits.”

When Thompson joined Birmingham Heart Group and started spending much of his time at St. Vincent’s East, one of his first priorities was making sure the protocol was available for his patients.

“We launched the program at St. Vincent’s East in January of 2009, just after UAB launched theirs. Now this therapy is available at every hospital in Birmingham,” Thompson said. “The challenge is if you have a heart attack in a rural area where a small local hospital isn’t likely to be able to offer the protocol.

“It takes both cooling and a 24-hour cath lab where you can clear the blockage to improve survival rates. As of now, Medicare doesn’t cover cath labs unless a cardiac surgeon is available if surgery is required. There simply aren’t enough cardiac surgeons to staff every hospital, and we can’t graduate enough, even if every small town had a population large enough to sustain a practice.”

Access to therapeutic hypothermia is likely to expand with time, but as of now the takeaway message for clinicians is to make sure patients understand the importance of exactly what Thompson and the other ten cardiologists at Birmingham Heart Clinic tell their patients.

“If you’re having heart symptoms, call 911 and get EMS involved. They know which hospitals have the hypothermia protocol and a cath lab available that isn’t backed up,” Thompson said. “So many people with a heart emergency arrive at the hospital in a car, either driving themselves or having a family member drive them. Maybe they are afraid they will be embarrassed if it turns out to be nothing, or that they can’t afford to spend money on an ambulance they may not need.

“What they don’t realize is that up to a third of people experiencing an acute heart attack will arrest before they reach the hospital. You can’t do CPR on yourself, and it’s hard to do it on someone else in a car and do it long enough to reach a hospital. It’s exhausting work. Worse yet, if you get there and they have to send you elsewhere, you lose vital time waiting for them to get an ambulance.”

For hospitals considering a therapeutic hypothermia program that may be reluctant because of budget concerns, Thompson has this advice.

“There are several techniques for cooling that work. If you have the budget, you can purchase equipment that cools and monitors temperatures for you and requires less staffing. But the old-fashioned way works, too. It can be as simple as saline and ice packs. The key is controlling temperature—not too cold, not too warm. That takes more staff if you don’t have automatic monitoring.

“What’s important is to just do it. Therapeutic hypothermia saves lives.”